Vibration generator



14,- 1942. HANCOCK 2,289,961

VI BRAT ION GENERATOR Filed May 6, 1939 Invent or: John E. H an cock,

H is Attorney.

Patented July 14, 1942 I i I VIBRATION GENERATOR John E. Hancock, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application May 6, 1939,-Serial No. 272,179

3Claims.

My invention relates to systems for the generating of mechanical vibration, or vibration motors or devices, of the moving coil type for the vibration testing of materials over wide ranges and amplitudes of vibration.

It is the general object of the invention to pro} vide an improved vibration device of the above type which is capable of converting large electric power into mechanical vibrations of relatively high frequency without damage to the moving system or other parts of the device.

It is a particular object to provide in the vibration device an improved pickup coil' arrangement for generating a small voltage proportional to the velocity of motion of the moving system and in which substantially no undesired voltable power or other devices (not shown) associated with the vibration device. A pin it is provided adapted to lock the moving system while test pieces are being attached to drive rod 9.

Referring more particularly to the cross-sectional view of Fig. 2, the electromognet having 7 the top, bottom and side plates 2, 3 and l com-- prises an annular pole piece I connected to the age, due to external magnetic fields, isgenerated in the pickup coil.

It is a further object to provide an improved moving system for the vibration device.

It is another object to provide an improved locking means for the moving system to permit rigid mounting bf test pieces on the device with-.

out danger of damage to the moving system The novel features which are considered to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing wherein Fig. 1 is a perspective view of a vibration device embodying my invention, and Fig. 2 is a cross-sectional view of the embodiment illustrated in Fig. 1.

Referring to the perspective view, Fig. 1, of the "vibration device embodying my invention, it will be understood that th moving system within the vibration device is supported by the frame I comprising the top, bottom, and side elements or plates 2, 3 and 4 of an electromagnet. A domelike structure 5, or structure in the form of the frustrum of a cone, mounted on the top plate 2 I serves to protect the drive coil or moving coil portion of the moving system from injury and also provides a mounting means for an upper bearing 6 through which-a sleeve 1 and a key 8, attached to the upper end of a drive rod 9 proiecting upwardly 'of the vibration device and threaded for the attachment thereto of test pieces, are slidable. A front plate. II) which is connected to the frame I carries terminals l2 and I3 for attachment of field, drive, and pickup coils, enclosed within the frame, to suittop plate 2, and a central core l6 of cylindrical form projecting upwardly through the pole piece I 5 and spaced therefrom to form an annular airgap I]. A field coil |9. surrounds the core I3.

The moving system comprises the above mentioned drive rod 9, a moving coil or driving coil structure IS, a bar magnet 20, a polepiece 2| for the magnet 20', the upper'bearing sleeve 1 which also functions as a drive coil locking sleeve, the key 9 fastened to sleeve 1, a coil locking cone 22, and a lower bearing member 23. The latter bearing member 23 projects through and is slidable in a lower bearing 24 mounted on the lower end of core IS.

The driving coil structure |9 comprises a cylindrical lower portion 25, in which is embedded a driving coil 26 within the air gap I1, and a coneshaped upper portion 21 locked rigidly to drive rod 9 by clamping between locking sleeve 1 and locking cone 22. The sleeve 1' and cone 22 are screwed to the drive rod. The upper end of core I6 is of concave or hollowed out form, and in thespace 28 enclosed between the cone-shaped upper portion 21 of driving coil structure I9 and the upper end of core I6 is mounted a helical centering spring 29 the upper end of which is fastened to locking cone 22 and the lower end to a spider30 mounted on the core I 6. Openings 3| are provided in dome structure 5, and openings 32 in bearing and locking sleeve I and rod 9,

- the moving systeni is centered by spring 29.

The rod 9 extends partially through a central opening 33 formed through the core IS. The bar magnet '20 is mounted in a recess 34 formed in the lower end of the rod 9 and the pole piece 2| is connected to the rod and in contact with the magnet. The lower end of the pole piece 2| is connected to the bearing member 23 which is of non-magnetic material. Adjacent to the pole piece 2| a pickup coil 35 is mounted on the wall of the central opening 33 of core l6.

In operation of. the vibration device, the pin H is inserted in the openings 3| 0t dome 5 of the fixed structure and openings 32 of sleeve 1 and rod 9 of the moving system, in order to lock the shown)" is being. attached to the upper end oi drive rod 9. The test piece may, therefore, be attached rigidly to rod 9 without unduly straining the key 8 which cooperateswith bearing The pin it is then removed, leaving the moving system, centered by spring 29, free to vibrate in linear motion. Field coil 18 and drive coil 26 are next energized respectively from suitable direct current and alternating current sources (not shown). The moving system then vibrates longitudinally at a desired frequency, being guided y 'moving system. in place while a test piece (not by the widely spaced bearings 6 and M, mounted respectively at the top of the dome structures and the lower end of core It of the magnet structure, and being prevented from rotational movement by the key 8 slidable in thebearing 6.

It willbe noted, that the moving system, com- I Q prising the driving "coil structure having the cylindrical coil supporting portion and the coneshaped upper portion, is extremely rigid while being also, extremely light. It has been found that with this construction of the moving system the vibration device operates on large power in-' put with-high efllciency, and that test pieces attached to the drive rod may be vibrated at relatively high frequencies and with relatively large form and construction of the dri'vingcoil structure ensures rigidity and lightness in the moving system, thearrangement is at the same time very compact, the centering spring being mounted in the space enclosed between theupper concaved face of the cone and the cone portion of the .driving coil structure.

. As the drive rod pole piece 2i of permanent magnet is vibrated 9 vibrates longitudinally, the

amplitudes of vibration. Further, while the November 6, 1941, which is a division of my pres ent application.

" My invention has been'described herein in a particular embodiment for purposes of illustration. It is to be understood, however, that the invention is susceptible of various changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

. What I claim as new and desire to secure by Letters Patent of the United States is: .1. In a vibration device,'the combination with 'a frame structure comprising a central core having an axial aperture therethrough, and a drive rod adapted to vibrate longitudinally and having a portion; extending within said aperture, of a magnet mounted in the extremity of said portion, a pole piece connected to said extremity and in contact with said magnet, a bearing connected to'said core, a bearing member connected to said pole piece and slidable in said bearing,

anda pickup coil in operative relation with 'saidpole piece and mounted on the wall of said aper-' ture. A

2. In a-vibration device, a frame structure having a relatively long and narrow aperture therethrough, and a drive element adapted to vibrate relatively to said structure and within said. aperture, a magnet substantially shorter than said element carried thereby in a recess formed in an end portion thereof entirely within said aperture, a-pole piece mounted on said end relatively to fixed pickup coil 35, a small voltage being thus generated in, the latter coil. This voltage is proportional to the velocity of motion of the drive rod, and due to the shielded position portion of said drive element and in contact with an end face of said magnet, and a pickup coil in operativerelation with said pole piece, said coil being mounted on said frame structure within said aperture and adjacent to said pole piece, whereby said coil is shielded by said frame struc' ture from outside magnetic fields.

of th coil inside the massive iron structure of the electro-magnet assembly, only a very small or negligible voltage will be induced in coil 35 due to any external magnetic fields. The small voltage generated in the pickup coil 35 by the -vibration of magnet 20 may be used for any suitable purpose,'for example, to operate a vibration velocity meter, or as the input to an amplifier which supplies'drivin'g coil 26,. in order to obtain self-sustained oscillations of the moving system at resonant frequencies.

The vibration motor, hereinabove described,

is claimed in application, Serial No. 418,077, filed 3'. In a vibration' device, aframe structure comprising a central core having a relatively long and narrow axial aperture therethrough, a 1 drive rod adapted to vibrate longitudinally insaid aperture, said rod having a recess formed therein at an end portion thereof entirely within said aperture, a magnet of short length relative to said rod mounted in said recess, the walls oi. said recess enclosing all of said magnet except an end ace thereof, a pole piece mounted on said in contact with-said end face, of said magnet, and a pickup coil adjacent to and in operative relacorms. HANCOCK.

end portion of said rod within said aperture and tion with said pole; piece and mounted on the wall-of said aperture. 1 

